Rear derailleur only shifting to halfway

mathie

Hi
My rear derailleur is only shifting from the biggest ring to midway on the cassette.
Any ideas what to look at to fix it?
Thanks
M

martyc5674

When shifting down the block(up in gears) your shifter is feeding cable towards the derailleur...the spring in the derailleur moves the derailleur outwards taking up the slack in the cable.
Its highly unlikely your limit screws need adjusting to that extent so keep away from these for the time being at least as i assume it was working before...its more likely a snagged inner cable/stiff derailleur hinge point/or possibly a broken spring.

Shift down as far as it will go...then shift another 2 gears say and tug the derailleur outwards and it might point you in the right direction...if your seeing slack anywhere in the cable run between derailleur and shifter then try and figure out whats preventing the derailleur from taking up the slack.
If theres slack in the section nearest the derailleur then the problem is with the derailleur.

Marty.

dub_skav

I had a similar problem, but I knew the cause.
Derailleur had jumped into rear wheel while cycling and took quite a bit of freeing.
Once free, it partially worked and I was able to finish my cycle. Turns out I had bent the derailleur hanger and it needed replacing.

However, if you have not banged it badly or had any kind of accident then the above post is the most likely explanation.

07Lapierre

did you install a new gear cable recently?

iwillhtfu

07Lapierre wrote: »

did you install a new gear cable recently?

If you did you may not have set the shifter it's start point when you fitted the cable.

If it's worked ok up to this point the cable may be damaged or the derailleur/cable getting caught on something or possibly a broken/weak spring.

07Lapierre

Maybe the cable anchor bolt is loose and the cable has slipped?

hesker

07Lapierre wrote: »

Maybe the cable anchor bolt is loose and the cable has slipped?

That would have the opposite effect I'd say.

First off I'd disconnect the cable at the rear der and check with your hand that there is good movement across the whole width of the cassette. If not check why not.

With the cable disconnected check how well the shifting works to move the cable. If it gets stuck at any point the cable could be snagging.

martyc5674

hesker wrote: »

That would have the opposite effect I'd say.

First off I'd disconnect the cable at the rear der and check with your hand that there is good movement across the whole width of the cassette. If not check why not.

With the cable disconnected check how well the shifting works to move the cable. If it gets stuck at any point the cable could be snagging.

Id hold off on disconnecting the cable just yet...given the OP has asked this relatively basic mechanical question im sure they wont want to have to go indexing.(no disrespect to OP intended)

Marty.

hesker

martyc5674 wrote: »

Id hold off on disconnecting the cable just yet...given the OP has asked this relatively basic mechanical question im sure they wont want to have to go indexing.(no disrespect to OP intended)

Marty.

Indexing is a pretty basic activity and nothing to be afraid of. Without pics the steps I propose will at least help the daignosis.

Limestone1

It's been a while since I've seen a link to Sheldon's site here so maybe not everyone is aware of all of these guides he put up.Some very good info and easy to follow .

http://sheldonbrown.com/derailer-adjustment.html

ted1

I'd look for a sticky cable. Is the cable loose at the derailleur side or if you pull it is does more cable come out outer cable.
Or your derailleur may be bent , might it have got a bang ?